Known mass spectrometers measure and report a value of mass to charge ratio for analyte ions in a sample. The determined mass to charge ratio is taken to be representative of the sum of the masses of the individual atoms present in an analyte molecule plus or minus the rest mass of one or more electrons (depending upon the charge state and polarity of the molecule when measured). The unit of mass to charge is based upon one mass unit being 1/12 of the mass of the most abundant isotope of carbon (12C) and one unit of charge being equal to the charge of an electron.
Conventional mass spectrometers process mass spectral data and calculate the mass to charge ratio of detected ions. However, the accuracy of a mass to charge ratio measurement will be dependent upon the particular type of mass analyser used, the quantity of analyte sample and the conditions under which a particular sample is mass analysed.
Although some conventional mass spectrometers are able to measure the mass to charge ratio of an ion to a relatively high precision and accuracy, conventional mass spectrometers are not able to determine the accuracy of each individual mass to charge ratio measurement relating to an unknown sample.
However, without an estimate of the accuracy of a mass to charge ratio measurement it is uncertain what range of mass to charge ratio should be considered when using, for example, a database of atomic elements and their isotopes to determine possible elemental compositions which will have mass to charge ratios substantially similar to that of the analyte ion. Similarly, it will also not be known what range of mass to charge ratio should be considered when searching a database of known molecules to find a match for an analyte ion. It will be appreciated that if a relatively wide mass to charge ratio window needs to be considered then the number of possible candidate ions dramatically increases.
It is therefore desired to provide an improved method of mass spectrometry and an improved mass spectrometer.